I saw The Haunting by dumb luck one Saturday morning on TCM. I remember the unique cinematography really caught my attention.
Both The Exorcist and The Haunting are on Scorsese's top list of scariest movies (pretty sure he nuances scary from horror). I have to admit to not having seen about half this list.
Scorsese's Scariest Movies:
The Exorcist - 1973
The Haunting - 1963
The Isle of The Dead - 1945
The Uninvited - 1944
The Entity - 1982
Dead of Night - 1945
The Changeling - 1980
The Shining - 1980
Night of the Demon - 1957
The Innocents - 1961
Psycho - 1960